Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$106.94	12.786%	$120.6133	$120.61	$120.60	$120.60
Purchase #2	$163.27	10.415%	$180.2746	$180.27	$180.25	$180.30
Purchase #3	$69.32	4.357%	$72.3403	$72.34	$72.35	$72.30
Purchase #4	$155.98	3.724%	$161.7887	$161.79	$161.80	$161.80
Purchase #5	$106.81	4.740%	$111.8728	$111.87	$111.85	$111.90
Purchase #6	$100.64	3.125%	$103.785	$103.79	$103.80	$103.80
Purchase #7	$222.53	12.727%	$250.8514	$250.85	$250.85	$250.90
7 purchase totals =	$925.49		$1,001.5261	$1,001.52	$1,001.50	$1,001.60